Functional assessment of ADL/IADL plays a vital role in the medical management and rehabilitation of the elderly. For individuals, assessment provides the key to accurate identification of problems and the implementation of appropriate remedial actions. For society, ADL/IADL assessment serves as a uniform measure of illness severity and functional outcome of health care interventions, regardless of diagnosis, and hence holds promise for the judicious and equitable distribution of health care resources. However, the results of various assessment methods may lead to differential treatments and therefore differential outcomes. Thus, reliable and valid ADL/IADL assessment methods are essential for patient care decisions as well as health care policy. The primary aims of the proposed study are to compare the functional outcomes of 5 common methods of assessing ADL/IADL in the elderly to compare their concurrent and predictive validities, identify factors that account for differences among outcomes, and explore their cost- effectiveness. This study will provide data about the relative merits and costs of the 5 assessment methods when accuracy and ability to detect change are taken into consideration; the extent to which the methods can be used interchangeably; and the degree to which the outcomes accurately represent the ability of frail, community-based older adults to perform ADL/IADL tasks in their own homes. The 5 methods include 3 subjective (self-report, proxy report, clinical judgment) and 2 objective methods (situational performance testing conducted in a health care setting and in subjects' homes). In-home testing serves as the criterion method, because the home is the independent living site. A health status indicator serves as an external, objective criterion measure. Samples will be drawn of older adults, 75-84 years of age, with depression, dementia, cardiopulmonary disease, and osteoarthritis, who are living independently in the community. These diagnoses were selected because they are highly prevalent in the older population and represent affective, cognitive, generalized physical, and discrete physical impairments, respectively. A sample of "well" elderly will serve as a comparison group. A total of 275 subjects, 55 in each of the 5 groups, will be assessed initially and 6 months later.